Jeff,
the SQRL app can automatically hand back off to the browser.
google's Smart Lock app does exactly this and it works very well. You should look into that. It's feature request #7 on your list and your note says it's impossible. It isn't.
I agree it certainly gives a good user experience.
I don't think I said it was impossible

Just that it was not possible to target a specific tab in a specific mobile browser. It seems that no one cares about opening a tab for every URL these days anyway. That certainly seems to be how Smart Lock is working. The tab that started the auth does not get control back, another tab is launched with the logged-on session.
I will certainly have a look at how smartlock is detecting which browser the auth request came from.
Thanks for the heads up.